1. Field of the Invention
The present invention relates to an information recording medium on which sector data generated from an ECC (Error Correction Code) block structure is recorded. The present invention also relates to an information recording apparatus for recording sector data generated from the ECC block structure. Furthermore, the present invention relates to an information reproduction apparatus for reproducing information an a recording medium on which sector data generated from an ECC block structure is recorded.
2. Description of the Related Art
In recent years, the standards (physical and logical standards) for existing read-only and rewritable DVDs have been created. The standards describe an ECC block structure appended with parity codes for error correction as a data structure to be recorded on an optical disk (information recording medium). In existing DVDs, data having an ECC block structure common to both read-only and rewritable optical disks is recorded. Also, the application standards that describe the recording format in the application layer upon recording AV (Audio/Video) information or stream information on existing DVDs have been created.
In the physical standards, the minimum unit of user information to be recorded on an optical disk is 2048 bytes, and this recording unit is called a physical sector. Data in the physical sector include a data ID that records a sector number or the like, an error detection code IED (Data ID Error Detection code) for the data ID, user information, and an error detection code EDC (Error Detection Code) for data in the physical sector. As an error correction scheme for improving the reliability of data recorded on an optical disk, a “REED Solomon product code” scheme is adopted, and an ECC block structure appended with PI (inner-code parity) data and PO (outer-code parity) data is formed. One ECC block consists of data for 16 sectors. The technique that pertains to the ECC block structure is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 10-172243.
In the present specifications, data contents or data structure including a data ID and parity data is called “data”, and user information (=Main data) to be recorded is called “information”. Also, data contents or information contents directly recorded in a physical sector on an optical disk are called “physical sector data” (=physical sector data block) or “physical sector information”. One item of physical sector information has a size of 2048 bytes.
The logical standards define the data structure associated with user information to be recorded on an optical disk when viewed from the host computer side which is connected to an interface of an information reproduction or recording apparatus. The minimum unit to be exchanged between the host computer and information reproduction or recording apparatus is defined as a logical sector, and in the present specification, the contents of user information corresponding to the logical sector are called logical sector information. The logical sector information has a size of 2048 bytes in correspondence with that of the physical sector information.
The contents of the logical sector information basically match those of the physical sector information. However, since the physical layer defined in the physical standard and the logical layer defined in the logical standard are different layers, the contents of the physical sector information may be different from those of the logical sector information in practice. That is, the host computer and information reproduction or recording apparatus exchange information using 2048-byte logical sector information as a minimum unit, and information obtained by processing this logical sector information may be recorded as physical sector information on an optical disk.
The minimum unit of video object information or audio object information transferred between the host computer and information reproduction or recording apparatus is also 2048 bytes in correspondence with the logical sector size. According to the application standards, video object information and audio object information are broken up into 2048 bytes, and are multiplexed in the format of a pack structure as a minimum unit upon being recorded on an optical disk. That is, audio/video information to be recorded on a recording medium is segmented along the time axis, and video packs that store video object information and audio packs that store audio object information are distributed while being mixed. In this case, the video or audio pack information itself corresponds to the contents of the logical sector information.
The minimum unit of recording stream information is called an SOBU (Stream Object Unit), and one SOBU size is defined to be 32 logical sectors or 2 ECC blocks.
In existing DVDs, error correction can be made up to a maximum burst error length of 6 mm on an optical disk. In next-generation DVDs, the data bit length on an optical disk (recording medium) becomes small since the data recording density increases. Assume that the data bit length is proportional to the wavelength of light used in an optical head of the reproduction or recording/reproduction apparatus, and is inversely proportional to NA (Numerical Aperture). In this case, if the next-generation DVD has an optical wavelength of 405 nm and NA=0.85 compared to the existing DVD having an optical wavelength of 650 nm and NA=0.65, the error-correctable burst error length on an optical disk (recording medium) is considerably reduced to 2.9 mm.6×(405÷650)×(0.65÷0.85)=2.9
Therefore, the next-generation DVD requires a technical means for assuring an error-correctable burst error length of 6 mm or more as in the current DVD.
When the correctable burst error length is greatly improved for the next-generation DVD while exploiting the REED Solomon product code technique as the ECC block structure, the following problems (1) to (2) are posed, and it is impossible to greatly improve the correctable burst error length by only changing the size of the REED Solomon product code of the existing DVD.
(1) The maximum size of a REED Solomon product code that corrects errors for respective unit bytes is limited to 256 rows×256 columns. In the existing DVD, the maximum size is 208 rows×182 columns. The existing DVD has an optimal structure within the limit range of 256 rows×256 columns, and it is difficult to greatly improve the correctable burst error length by merely changing the size.
(2) The main data information encoding efficiency cannot be greatly reduced compared to the existing DVD. It is possible to improve the correctable burst error length by increasing the PO size in an ECC block. But when this is done, redundancy which depends on the PO size increases and the main data information encoding efficiently drops considerably. The existing DVD has main data information encoding efficiency of 87% as well as redundant data such as a data ID and the like in the physical data. Hence, in the next-generation DVD, an encoding efficiency of around 87% needs to be assured.
(3) An appropriate physical data structure must be guaranteed. As a method of greatly improving the correctable burst error length and of assuring high main data information encoding efficiency, a method of largely increasing the PO size and reducing the PI size accordingly may be readily devised. However, in order to assure high-speed data access on an optical disk, the data ID must be arranged at the head in the physical sector data, and an interleaved arrangement of PO data in respective physical sectors is required for this purpose. However, to attain this, it becomes difficult to change the PO size to an arbitrary value.